Cage flushing times were measured by Rhodamine-WT dye injection in a heavily fouled, 12 m square salmon pen stocked at approximately 4.7 kg/m3. A five port manifold was used both to inject the dye and withdraw water samples for concentration analysis. Exponential decay curves were fitted to dye concentrations after an initial period of about 3 minutes required for the dye to reach a homogeneous distribution within the cage following injection. Eight runs were made under various conditions of incident current. Two of the eight runs had to be discarded as flushing was too rapid for the dye to reach homogeneity, a condition necessary for the exponential fits to be meaningful. Most rapid flushing occurred for currents across the open side of the pen vrs currents running along the length of the multiple pen array. Fitted exponential time constants ranged from about 1 to 7 minutes. Estimates were also made of the mixing within the cage due to various levels of fish activity. The results have application to both farm design and estimation of the environmental impact of parasite treatments.
Power spectra of dissolved oxygen time series observations from both within a mariculture site and at a control site were briefly presented. Diurnal and tidal signals were evident.
Gary L. Bugden Maritimes Region Fisheries and Oceans Canada Bedford Institute of Oceanography P.O Box 1006 Dartmouth,N.S. Canada B2Y 4A2 Telephone (902) 426-2960 Fax (902) 426-7827 Email g_bugden@bionet.bio.ns.ca